How far would you goto save a life?

Watchmen explores the idea of justified sacrifice through the moral dilemmas of several "superheroes" in the 1980's.

Each super hero quantifies reasonable sacrifice differently.

Rorschach

The character Rorschach punishes evil whenever he sees it. This means there are generally many casualties along the way. To him this is necessary to enforce justice.

Doctor Manhattan

The character Doctor Manhattan, also known as Jon, experiences time differently than other characters due to a shift in his molecular make up. He views time as happening all at once instead of linearly. His view of the grander picture of things leads him to act without remorse because he believes that person was supposed to die.

Adrien Veidt

Adrien Veidt is Ozymandias, the most intelligent man alive, but also the most conceited man alive. He believes that he alone can reshape society in his image and create world piece. In his eyes there is no greater execution of justice but in order to reshape something he must break it first. To him, as long as he kills less than he saves, he is justified.

So is killing some okay in order to potentially save many?

In a sense, no.

Although you might be saving many people by killing the few, you are still slaughtering people. The fate of another shouldn't rest in someone else's hands. Each person should be responsible for their own destiny and natural forces should figure out the rest.

Is the sacrifice of the few sometimes necessary to save the many?

In a way, yes.

It'd be crazy to say let five people die to save one person but again, who is any one person to decide. No one person can handle the raw power of deciding who lives and who dies, they would go mad and be driven to do horrible things much like Adrien Veidt was. It was his simplification of sacrifice into mere metrics that drove him to commit an act most heinous.